Field of the Invention
The present invention relates to radio mesh systems using satellites in random orbits in communication with ground stations including ground-based receivers and transmitters for cellular telephone communications and Internet connections, and more particularly, to systems and methods of automatically establishing radio routes between ground stations using one or more unguided or substantially unguided satellites deployed randomly or quasi-randomly in low-earth orbits.
Description of Related Art
A brief history of certain aspects of cellular telephony relevant to the present disclosure is set forth in U.S. Pat. No. 5,793,842, which names as an inventor Jerry R. Schloemer, who is also the present inventor. One early system architecture, still in use today, involved a limited number of tower-mounted transceivers (“drops”) and plural mobile radios (“cellular telephones”). In these early systems, and still in some cases today, a central computer controlled communications between land lines connected to the towers and the mobile radios. Implementing this system architecture required significant investment in infrastructure and computing power, especially as the increasing popularity and technical capabilities of cellular telephones necessitated increased system capacity and sophistication. An alternate system architecture involved using radio transceivers (“nodes”) mounted on existing structures, such as buildings and telephone poles. These architectures use nodes capable of receiving and transmitting signals to and from cellular telephones along a radio route among the nodes to drops at selected nodes. This came to be called a mesh network, an early example being the system disclosed in Cox, Donald C., “Wireless Network Access for Personal Communications,” IEEE Communications Magazine (December 1992), pp 96-115.
A particular challenge in implementing mesh systems was how to determine the best available radio routes for interconnecting the nodes. Generally, early mesh systems still required a central computer to make routing determinations, which added to system complexity and cost. Other approaches, such as that described in U.S. Pat. No. 4,937,822 to Weddle et al., involved a mesh system in which routes would be established automatically, that is, without a central computer. However, Weddle disclosed such a system only in a mesh in which the nodes are laid out in a regular rectangular grid and radio routing links can only be between nodes orthogonally adjacent to each other (that is, cater-corner links between nodes would not be permitted). The shortcomings of such a system will be immediately apparent to those skilled in the art, if for no other reason than in a real-world setting it would be very difficult, if not impossible, to distribute nodes in a strictly orthogonal, uniformly-spaced rectangular grid over a wide enough area to make the system practicable. Moreover, Weddle does not disclose in detail any algorithm by which the nodes would actually create a preferred radio route.
Against that background the present inventor's U.S. Pat. No. 5,793,842 disclosed a system and method of creating radio routes through a mesh of nodes that were not limited in their placement and did not require a central computer. The systems and methods described in detail further below in connection with the present invention take advantage of technology described in U.S. Pat. No. 5,793,842 relating to the creation of radio routes through plural, randomly located nodes and the transmission of communications using those routes. To avoid the necessity of setting forth here the details of these types of systems and methods, the disclosure in U.S. Pat. No. 5,793,842 relating to route creation, and digital and analog signal transmission using the routes thus created, is incorporated herein by reference as if set out in full.
The inventor improved on that technology in his later U.S. Pat. No. 6,459,899, which, among other things, describes a system that uses nodes with directional antennas to improve the route creation and communication transmission capabilities of the earlier system. This improvement solves complex issues presented by using nodes with directional antennas in the systems and methods described in the '842 patent, and thus takes advantage of the higher quality radio links achievable with directional antennas. The present invention also uses the technology disclosed in the '899 patent, and its descriptions of route creation are incorporated by reference herein.
Before the inventor's approach to creating routes through a radio mesh network with randomly distributed nodes and no central computer, others were proposing ways to provide worldwide cellular coverage using satellites for call transmission between earth-based originating and destination drops. An example of a satellite system that was actually commercialized is disclosed in various patents such as U.S. Pat. No. 5,274,840 to Schwendeman and U.S. Pat. No. 5,410,728 to Bertiger et al., both of which are assigned to Motorola, Inc. This system utilized satellites evenly distributed in a predetermined number of polar orbits as transceivers for signals between satellites and between satellites and transceivers on the ground. A sufficient number of satellites is used to provide coverage of the entire globe. However, in practice this system, which was commercialized by Iridium, had numerous drawbacks. One was that each satellite needed onboard thrusters, rocket fuel, and navigational hardware to maintain its desired orbit. This increased satellite size and weight, which increased the launch cost, as well as increasing the cost of the satellite itself. Also, to account for inevitable satellite failures, extra satellites would have to be maneuvered into a failed satellite's orbit, thus increasing the cost of the entire system by requiring extra satellites and their concomitant high manufacturing and launch costs. See, for example, “Iridium Satellite Constellation,” Wikipedia, https://en.wikipedia.org/wiki/Iridium (last visited May 9, 2017). Ground-based orbit and attitude control using complex computer technology further increased system costs. In the end, its drawbacks made the system commercially unviable for mass market applications, although it is believed to have found use in specialized areas such as military applications and reporting by journalists from remote areas.
In addition to maintaining each Iridium satellite in a particular orbital position relative to the earth and other satellites, the attitude of each satellite also had to be maintained within certain tolerances so that its antennas would be oriented for effective satellite-satellite and satellite-ground radio communications. One way of providing attitude control was using onboard thrusters, which present the drawbacks already discussed. Various mechanically-based inertial attitude control systems have been proposed, such as those described in U.S. Pat. Nos. 3,017,777 and 8,164,294, and in Chabot, J. A., “A Spherical Magnetic Dipole Actuator for Spacecraft Attitude Control,” Thesis for M. S. in Aerospace Engrg. Sciences, Univ. of Colorado, 2015. However, it is believed that these types of systems would not perform any better than rocket-based attitude control, while their mechanical complexity and onboard control systems would preclude significant savings in weight as compared to rocket-based attitude control.
The present inventor disclosed in his U.S. Pat. No. 5,566,354 a satellite cellular telephone system that improved on the Motorola-Iridium approach. The inventor's improved approach allowed the satellites to occupy random orbits. This eliminated the orbital control components of satellite systems that relied on each satellite being in a known location relative to the others, such as the Motorola-Iridium system or the wireless telephone/satellite system disclosed in U.S. Pat. No. 5,303,286. However, the random-orbit system described in the '354 patent has certain drawbacks, one of which is that the satellites still require attitude control to insure that the satellite antennas point in the correct directions. Nor, as discussed in detail further below, does it have the advantages of a true mesh system, as that term is used in this description.
Aside from the rapid spread of cellular telephone usage around the world in recent years, access to the Internet through computers and smartphones has become a necessity for businesses and individuals alike. It is difficult to do business or manage personal affairs effectively without access to Internet-based resources like email, electronic banking, investigative/search services, and many others. In addition, social media providers like Facebook and Twitter can only exist in areas of the world that provide Internet access. A satellite-based system presents an ideal way of making the Internet and cellular telephone service available in remote areas without blanketing a country with towers or installing land-based radio mesh nodes across vast areas. However, known satellite systems suffer from numerous drawbacks, some of which are discussed above, and none has been successfully commercialized to date. In fact, a low-cost satellite system would have the potential to replace tower-based systems and ground-based mesh systems altogether.